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G. W. DRAWB'AUGH. TELEPHONE TRANSMITTER. No. 298,677. Patented MaylS, 1884;

l gy g g INVENTQR ZU. OvMwah,

BY FOL/v *M H ATTOENEY @ITNESSES: me

lire rarns tribe.

arnar GEORGE WV. DRAWVBAUGH, OF EBERLYS MILL, PENNSYLVANIA, ASSIGNOR TO THE PEOPLES TELEPHONE OOMPANY,OF NEYV YORK.

TELEPHONE TRANSIl/IITTER.

SPECIFICATION forming part of Letters Patent No. 298,677, date d'May 13, 1884.

Application filed November 12, 1883. (N model.)

To all whom it may concern.-

Be it known that I, GEORGE l/V. DRAW- BAUGI-I, of Eberlys Mill, Cumberland county,

Pennsylvania, have invented a new and useful Improvement in Telephone-Transmitters, of-

which the following is a specification.

The invention relates to a carbon transmitter of that class wherein two electrodes are employed, one being fixed and the other being movable, the movable electrode resting on the fixed electrode by gravity; and it consists in the particular construction and arrangement of the electrodes hereinafter set forth and claimed.

In the accompanying drawings, Figure 1 represents a rear view of the instrument with the back board B broken away, so as to show the carbon on the rear side of the diaphragm. Fig. 2 is'a vertical section on the line x 00, Fig. 1. Fig. 3 is a detail view showing the carbons enlarged. Fig. 4 is a face view of the pivoted carbon. Fig. 5 is a view of a modification, showing the movable and fixed carbons relatively reversed in position, the pivoted carbon being secured to the diaphragm of the instrument instead of to the back board.

Similar letters of reference in the several figures indicate like parts.

A is a box or case. B is the back board. 0 is the cover, having a mouth-piece orifice, D. E is the diaphragm, which may be of any suitable material. Hand M are two blocks or pieces of carbon or other conducting material, having their proximate faces in contact, the plane of contact being inclinedat an angle, preferably, of forty-five degrees to the horizontal. One of these blocks is connected directly or indirectly to the diaphragm, so as to vibrate therewith. The other is secured to the back board or any other suitable support. One of the blocks is fixed rigidly to its support, while the other is pivoted or jointed in any suitable manner to its support, so that its free inclined end will rest by gravity upon the inclined face of the fixed carbon block. a b are the local-circuit wires, one having elec trical connection with the carbon M and the other with the carbon H by any suitable means, so that the current will pass to one carbon,

thence to the other, and thence through the primary of induction-coil P back to the battery, the secondary of the induction coil being in the main line. It is preferable to provide grooves or recesses, or both, in the contact-faces of the carbon blocks, as shown in Fig. 4, to prevent atmospheric pressure from interfering with their free movement.

. The above constitute all the essential requisites of the instrument, and the details of its construction and arrangement may be varied 6o indefinitely.

In Fig. 3 the upper carbon block is represented as hinged to the back board, while in Fig. 5 it is shown as hinged to the diaphragm. v In the particular machine represented in de- 6 tail in Figs. 1, 2, and 3, the fixed carbon is secured to the diaphragm and the movable carbon to the back board. In Fig. 5 the position of the carbons is reversed, the movable carbon being secured to the diaphragm and the fixed carbon to the back board.

Referring more particularly to Figs. 1, 2, and 3, attached directly to the diaphragm E, or to a supporting-block, F, secured thereon, is a metal bracket, G. This bracket holds a block of carbon, H, having a side or surface inclined at an angle, preferably, of forty-five degrees. To the back board is secured ablock,

F, to which is attached a metal bracket, I. This bracket may be secured, if desired, directly to the back board, the piece F being omitted. J is another metal bracket, pivoted by a metal pin, K, to the bracket I. Surrounding the pin K, and between the brackets J and I, are placed small washers L, of paper or other insulating material, to reduce the area of rubbing contact between brackets I and J. Held in the bracket J is a piece of carbon, M, having a side or surface inclined at an angle preferably of forty-five degrees. 0

In Fig. 5 the brackets I J and carbon M are shown attached to the diaphragm E and the bracket G and carbon H to the back board, 13.

The circuits in the instrument proceed as 5 follows: from the battery to binding-post 1, to contact-plate N, to contact-plate O, (secured to the diaphragm,) through wire a, bracket G, carbon H, carbon M, bracket J, pin K, bracket 1, wire I), to primary of induction-coil P, thence to binding-post 2 and battery. The secondary wire 0 c from the induction-coil I? proceeds by the binding-posts 3 4 to the line.

The operation of the instrument is as follows: The diaphragm E being set in motion by speech, the carbon attached to said diaphragm is caused to approach or recede from the carbon secured to the back board, the movable carbon being free to slide up and down on the beveled surface of the fixed carbon. The area of surface contact of said oarbons is thus varied, and at the same time modifications are produced in the pressure of said carbons, thus modifying the current passing through the electrodes in a manner suitable for telephonic purposes.

Induction-coil P may be held in place by a metal bracket, R.-

I am aware that it is not new to employ a cylindrical fixed electrode attached to a diaphragm, in combination with a series of thin pivoted triangular plates resting their edges upon said fixed electrode, as shown in patent to Olmsted, No. 252,132, January 10, 1882; also, that a tubular holder carrying a gravitating electrode has been pivoted to a dia phragm for adjustment purposes, as shown in v patent to Daniel Drawbaugh. No. 290,980, December 25, 1883. These constructions I do not herein claim.

I claim as my invention- 1. In a telephone-transmitter, the combination of a diaphragm, an electrode inclined or having an inclined face placed at an angle, preferably forty-five degrees, the said elec= trode being pivoted or hinged to said diaphragm, and a second electrode inclined or having an inclined face to correspond to the inclination or to the inclined face of the firstmentioned electrode, the said second electrode being rigidly secured to a support and receiving upon its inclined face the inclinedface of the first-mentioned electrode, which rests upon it by gravity, substantially as described.

2. In a telephone, two electrodes inclined or having faces inclined at an angle, preferably, of forty-five degrees, one electrode being rigidly fixed and the other electrode hinged or pivoted, the last-mentioned electrode resting, by gravity, with its inclined side or face upon the inclined side or face of the fixed electrode, one of said electrodes being attached to the diaphragm and the other electrode being rigidly held in a support, substantially as described.

3. The combination of the diaphragm E, carbon H, carbon lVI, bracket G, bracket J bracket I, ameans of hinging or pivoting said brackets I and J, and a support, 13, substantially as described.

, GEORGE \V. DRAWVBAUGH.

Witnesses: V

FRED. M. Orr, M. W. JACOBS. 

